Safety plug for flatirons



W. T. HOOFNAGLE SAFETY PLUG FOR FLATIRONS Original Filed Sept. 28, 1921 March 19, 1929.

Patented Mar. 19, 1929.

UNITED STATES PATENT OFFICE.

WILLIAM T. HOOFNAGLE, OF GLEN RIDGE, NEW JERSEY, ASSIGNOR TO THE COMFO ELECTRIC IRON COMPANY, OF GLEN RIDGE, NEW JERSEY, A. CORPORATION OF NEW JERSEY.

Original application filed September 28, 1921, Serial No. 503,789. Divided and this application filed December 8, v19:24.

This invention relates to improvements in safety devices for preventing the overheating of electric fiat irons. The present application is a division of my original application Serial Number 503,789, filed September 28, 1921. In carrying out the invention, I provide a socket on or within the iron adapted to receive a plug which is outwardly the same as the threaded fuse plugs commonly used for protecting house lighting circuits. The socket is open at the bottom and when the plug is threaded into the socket its base contact engages the body of the iron and is heated thereby when the iron is in use. The plug has the usual side contact, in the form of athreaded shell, which engages a similar shell within the socket. Within the plug, I arrange a fusible element directly engaging the base contact and adapted to be melted by the heat of the iron when the latter is left standing with the current on and becomes dangerously hot. In addition to this fusible element, I provide, within the socket, a filament which can be heated to a dull red by the electric current while the current is on and serves as a visual signal to the operator, to indicate whether the current is on or oil. This filament and the fusible element are connected in series with one another and with the heating resistance in the iron. 'It is difficult to tell, after an iron has become heated, whether the current is on or off and frequently an operator, after setting an iron aside, will, through habit, cut off the current at the key switch, or push button switch, usually employed, and then forget whether it has been turned off or not and operate the switch again, which will turn the current on. The filament, in the present invention, will always indicate whether the current is on or off. If the operator, through carelessness, fails to open the switch when the iron is not in use, then the iron will become overheated, and the fuse will melt at or before the time when the iron reaches a scorchin temperature. The melting of the fuse wi open the circuit through the filament as well as the heating resistance. Possible damage from fire will thus be averted, and as no current can be passed through the filament by turning the switch, the operator will know from a glance at the plug that the fuse has blown and that it must be replaced by another.

Serial No. 754,642. 7

In the accompanying drawing,

Fig. 1 is a top plan View of a flat iron, partly broken away, and with the upper casing and handle removed, showing my invention applied thereto, the heating resistance being shown in dotted lines;

Fig. 2 isa section of Fig. 1; and,

Fig. 3 is a vertical section through the plug.

Referring to Figs. 1 and 2 of the drawing, A represents the iron comprising a metal base 1, a heating resistance 2, resting upon the base, and a metal bod 3 which rests upon the heating element an is clamped to the base in the usual manner. One end of the resistance is connected to a terminal 23 and the other end is grounded on the body 3, at g. In the body 3 is a recess 4, within which is arranged a socket 8,.0f insulating material, having an internal annular threaded contact member 5. A hollow screw plug 6 is provided with a threaded side contact 6, for engaging the contact 5, and with a base contact 7, which, when the plug is in place, rests against the metal body 3.

The plug is provided with a transparent window 8. Within the plug is arranged a filament 9, of non-oxidizable material, such as vplatinum, and this filament is connected to the side contact 6 of the plug and to a body of fusible material 10 on the base contact. The threaded contact in the vsocket is connected by a conductor 11 to the terminal 22, and it will be evident that the current fiowing from the terminal at to the terminal t will flow through the resistance, the fuse and the filament in series. The current for heating the iron thus flows through the filament and the latter is proportioned so that it will heat to a dull red while the current is on. If the iron becomes overheated, the fusible material will melt, from the heat of the iron, and this will break the connection between the filament and base contact and interrupt the current through both the filament and the heating resistance. In order to use the 1I0I1 thereafter, it is necessary to replace the plug with another similar plug.-

The filament will glow as long as current flows through the heating resistance, and by observing the filament, the operator can always tell whethert-he current is on or off.

While in use the iron will not become overheated, as the heat is dissipated in the fabrics over which the iron is passed. If the iron is out of use for a short time, and the current is left on, the temperature will rise. It the operator'is careless and does not turn off the current when the iron is out of use, the fuse will blow and out 01f the current-before the iron becomes dangerously hot.

Vhat I claim is:

1; A plug for the purpose described comprising a hollow closed body having base and side terminals, said base terminal extending through the wall of the plug, a fusible element within the plug engaging the base ter minal and adapted to melt at a relatively low temperature, and a lighting filament within the plug connected in series with the fuse and the side contact of the plug.

2. In an electrically heated flat iron, 2. heating resistance, a metal body adapted to be heated by the resistance, a socket on the iron, a hollow plug fitting said socket and having a terminal engaging said body, a fuse element in the plug engaging vsaid terminal and adapted to melt at relatively low temperature and a lighting filament in the plug, said resistance, fuse element and filament being in series with one another.

In testimony whereof I hereunto affix my signature.

WILLIAM T. HOOFNAGLE. 

